<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.
0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="js/jquery-2.1.1.min.js"></script>
    <title>Document</title>
    <script>
            // ajax 提交
            function mysub(){
                // 1. 判空
                var username = jQuery("#username");
                var password = jQuery("#password");
                if(jQuery.trim(username.val())==""){
                    alert("请先输入用户名");
                    username.focus(); // 光标重置到此元素
                    return;
                }
                if(jQuery.trim(password.val())==""){
                    alert("请先输入密码");
                    password.focus(); // 光标重置到此元素
                    return;
                }
                jQuery.ajax({
                    url:"/test/login2",
                    type:"POST",
                    contentType:"application/json",
                    data:JSON.stringify({"username":username.val(),"password":password.val()}),

                    success:function (result){
                        alert(JSON.stringify(result));
                    }
                })

            }
    </script>
</head>
<body>
<div style="text-align: center;">
    <h1>登录</h1>
    ⽤户：<input id="username">
    <br>
    密码：<input id="password" type="password">
    <br>
    <input type="button" value=" 提交 " onclick="mysub()" style="margin-top: 20px;margin-left: 50px;">
</div>
</body>
</html>